In recent years, discussions have been taking place to enable a spectrum assigned for primary usage to be used for a secondary communication service depending on the use condition of the spectrum. For example, the standard specification for allowing an unused channel contained in a spectrum of the U.S. digital TV broadcast (TV white spaces) to be available for a radio communication has been studied in the IEEE802.22 working group (cf. Non-Patent Literature 1). Further, according to the report from the FCC (Federal Communications Commission) in November 2008, the discussions are directed toward permitting secondary usage of TV white spaces by using communication devices that have been authorized by fulfilling a certain criterion (cf. Non-Patent Literature 2). Further, there are moves, led by the EU, afoot to universally allocate a dedicated control channel called the CPC (Cognitive Pilot Channel) for making DSA (Dynamic Spectrum Access). Furthermore, technological studies for a secondary usage system that makes DSA are also being progressed in IEEE SCC (Standards Coordinating Committee) 41. Further, as another example of secondary usage of a spectrum, there is a case where a secondary communication system is constructed using a simpler communication protocol in a service area of a majority system that uses a non-licensed spectrum. For example, it is assumed that when a WiFi (registered trademark) system that uses an ISM (Industry-Science-Medical) band is a majority system, a secondary communication system is constructed using another simple communication protocol in its service area.
In such secondary usage of a spectrum, it is necessary to sense the surrounding communication environment in advance and confirm that a communication service related to secondary usage (which is referred to hereinafter as a second communication service) does not cause an adverse effect on a communication service related to primary usage (which is referred to hereinafter as a first communication service).